Answer to Question #12163 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I have a two-story garage built into the side of a hill. The lower level of the garage has no windows, and it contains a workshop. In the workshop, I have measured the average radon level over a four-month period to be about 160 becquerels per cubic meter (Bq m-3). Since this room has only intermittent use, say about one to two hours a day for a couple of days each week, would a P100 mask be adequate to filter out the radon particles?
Yes, the P100 filter would significantly reduce the amount of radon decay products that you would inhale, but there are additional factors to consider. If you have not measured other parts of the house, I would recommend doing so just to make sure there aren't some areas that have higher radon concentrations. Also keep in mind that radon entry does change with seasonal weather patterns, and a test in the heating season and another in the cooling season can determine when the radon is at its highest. While there is a stereotype that radon is always highest in the winter, there are factors that can cause just the opposite to occur.
If you have tested other parts of the house and the garage is the only area of concern, and the long-term average is approximately 150 Bq m-3, then a couple hours per week of exposure isn't thought to be of great concern. While it is true that the U.S. Environmental Protection Agency (EPA) set the U.S. action level at 4 picocuries per liter (150 Bq m-3),1 many of the EPA's health risk estimates were based on far greater exposures than you are describing.
That said, if you feel more comfortable wearing the mask, you can be assured that the P100 filter would significantly reduce the amount of radon decay products that you would inhale. However, the filter would not remove the risks entirely because all of the radon gas and some of the decay products would still pass through the filter. Controlling radon entry into the building is the preferred method for lowering radon exposure.
Shawn Price, Past President of the American Association of Radon Scientists and Technologists (AARST)
1 The radon concentration units are given here in picocuries per liter (pCi L-1, called traditional units) because that is the unit used by the EPA. However, the Health Physics Society has adopted the International System (SI) of units and these are given in parentheses.